1. Field of the Invention
The present invention relates to a developing apparatus for developing a latent image (an electrostatically charged latent image, potential latent image, magnetic latent image and the like) with a powder developer, which latent image is formed on an image bearing member such as an electrophotographic photosensitive element, electrostatic recording dielectric element, magnetic element and the like arranged in an image forming system (a copying machine, printer, displaying machine and the like) wherein an image is formed electrophotographically, electrostatically or magnetically. The present invention further relates to a process cartridge having such developing apparatus and adapted to be removably mounted to the image forming system.
2. Related Background Art
A conventional developing apparatus as shown in FIG. 1 comprises a developing container portion (first chamber) 10 including a developing roller or developing sleeve 11 for conveying a developer therealong and a metering blade 12 for regulating a thickness of the developer layer formed on the developing sleeve 11, and a developer container portion (second chamber) 20 formed integrally with the developing container portion 10. Between the container portions 10 and 20, a hard plate 21 is arranged as a partition. The partition plate 21 includes an elongated slit 22 formed therein and extending in a longitudinal direction of the plate (i.e., a direction perpendicular to a plane of FIG. 1), through which (slit) the developer container portion 20 communicates with the developing container portion 10. A developer agitating and conveying member 23 arranged in the developer container portion (second chamber) 20 can be turned around a pivot shaft 23a to agitate and convey the developer in the second chamber 20. Although not shown clearly in FIG. 1 for the simplicity's sake, a developer (one-component toner or two-component toner) is stored in the developer container portion 20.
When the developing apparatus is operated, the developing sleeve 11 in the developing container portion 10 is rotated in a counter-clockwise direction shown by an arrow at a predetermined peripheral speed by means of an appropriate driving means (not shown), whereas the agitating member 23 in the developer container portion 20 is turned continuously or intermittently in a clockwise direction shown by an arrow at a predetermined lower speed by means of an appropriate driving means (not shown). The developer (one-component toner, or two-component toner or toner component therein) in the developing container portion 10 (supplied from the developer container portion 20) is carried by the peripheral surface of the developing sleeve 11 to form the developer layer thereon, a thickness of which is adjusted by the metering blade 12. Then, as the developing sleeve 11 is rotated, the developer layer is brought into a developing station where the developing sleeve faces to an image bearing member (electrophotographic photosensitive rotary drum and the like) D. In the developing station, the developer (toner) on the developing sleeve 11 is transferred and adhered to the image bearing drum D selectively in accordance with a pattern of the latent image formed on the drum D to visualize (develop) the latent image.
By the rotation of the agitating member 23 in the developer container portion 20, the bridges and/or blocks included in the developer in the developer container portion 20 is destroyed or pulverized and, at the same time, the developer is gradually fed into the developing container portion 10 through the elongated slit 22 of the partition plate 21 to compensate for the used developer.
In such developing apparatus, in order to always maintain the quality of the developed image (or output image) at a predetermined constant level, it is very important that an amount of the developer (or a mixing ratio between the toner component and the carrier component (i.e., toner density) when the two-component toner is used) should be maintained always at a predetermined constant level by replenishing the used toner in the developing container portion 10 used in the developing operation with a new toner being supplied from the developer container portion 20 neither more or less. This is particularly important when the developer is the two-component toner. If the developer is supplied to the developing container portion 10 excessively, a powder pressure and/or toner density of the developer in the developing container portion 10 is increased, thus presenting a bad phenomenon such as excessive increase in the image density, fogging, scattering, smearing at image trailing end and the like, resulting in the decrease in the quality of the image.
On the other hand, if the developer is supplied to the developing container portion 10 insufficiently, the image density is decreased, thus worsening the quality of the image. Accordingly, the excessive or insufficient supply of the developer from the developer container portion 20 to the developing container portion 10 will lead to affect a bad influence upon the quality of the image.
The amount of the developer supplied from the developer container portion 20 to the developing container portion 10 depends upon a width W.sub.22 of the elongated slit 22 and a developer conveying or discharging force of the agitating member 23.
If the width W.sub.22 of the slit 22 is larger, there arises problems such as excessive supply of the developer, uneven supply of the developer, reverse flow of the developer from the developing container portion 10 to the developer container portion 20 and the like. For this reason, in order to supply the developer to the developing container portion 10 for easily maintaining the amount of the developer or the toner density of the developer in the developing container portion 10 always at a predetermined constant level, it is preferable that the width W.sub.22 of the slit 22 is selected to be smaller and the developer is gradually supplied from the developer container portion 20 to the developing container portion 10 through the narrower slit 22.
In the conventional developing apparatus of this kind, the partition plate 21 having the elongated slit 22 formed therein comprises a hard plate obtained by blanking or plastic moulding. While the width W.sub.22 of the elongated slit 22 can be optionally selected to be larger or smaller, if the width of the slit is selected to be smaller for the above reason, some agitating members 23 apply the greater resistance to the developer being pushed and passed through the slit 22 thus making the supply of the developer (through the slit) difficult, or some agitating members 23 urge or press the developer against the edge portions of the hard plate around the slit 22. Consequently, the developer is subject to the overload, with the result that the developer with the compressed solid lumps or blocks is supplied to the developing container portion 10, and/or the slit 22 is partially or wholly clogged or jammed by such lumps to present the insufficient supply of the developer.
In this connection, in the past, the width W.sub.22 of the slit 22 was selected to have a relatively large dimension in order to avoid at least the supply of the developer lumps (to the developing container portion 10) and the insufficient supply of the developer (to the developing container portion 10) due to the jamming of the slit 22, in disregard of the excessive supply of the developer, uneven supply of the developer and/or the reverse flow of the developer (from the developing container portion 10 to the developer container portion 20).
By the way, the toner is colored pulverized powder having an average diameter of 20 .mu.m or less, and thus, can easily be scattered even by weaker vibration, impact and/or wind pressure. Accordingly, when the developer is replenished or added to the developing apparatus by pouring the developer from an opened or unsealed developer package into the apparatus through a replenishing opening of the apparatus, unless the replenishing operation is carried out carefully, the developer (toner) is scattered out of the apparatus, thus smearing peripheral devices or elements and/or operator's fingers with the scattered toner.
In order to eliminate such problem of the scattering of the developer and to facilitate the handling of the developer, a developing apparatus obtained by integrally assembling the developing container portion and the developer container portion previously including the developer therein altogether and adapted to be removably mounted on the image forming system has been proposed and been practically used.
More particularly, such proposed developing apparatus is so constructed that a developer containing (storing) container portion previously filled with a developer confined therein is integrally mounted on a developer container portion incorporating a developer bearing member such as a developing roller or developing sleeve by which the developer is applied to an image bearing member to visualize a latent image, and that a developer supplying opening of (the developer containing container portion) communicating with the developing container portion is initially sealed by a sealing member (refer to the Japanese Patent Application Laid-Open No. 59-13262, U.S. Pat. No. 4,615,608).
In such developing apparatus, when it is not yet used, since the developer is maintained to be sealingly confined within the developer containing container portion, the developer can be effectively prevented from leaking and/or scattering out of the developing apparatus and from becoming wet or damp while the developing apparatus is being transported or stored.
In use, the sealing member sealing the developer supplying opening arranged between and communicating with the developing container portion and the developer container portion is removed by pulling it from outside of the developing apparatus to open the developer supplying opening. In this way, the developer flows from the developer container portion to the developing container portion through the opening, thus enabling the developing operation. In this case, since the unsealing of the sealing member and the supply of the developer from the developer container portion to the developing container portion are both carried out within the apparatus except the removal of the sealing member toward outside of the apparatus, the scattering and/or leakage of the developer out of the apparatus can be substantially prevented.
The developing apparatus of this kind is generally of a disposable type (i.e., when the developer has been used up, the apparatus is dumped). Accordingly, when the developer previously contained in the developer container portion has been used up, without replenishing additional developer, the whole developing apparatus, or a process cartridge (if the developing apparatus is assembled together with elements of the image forming system such as the image bearing member (photosensitive drum), cleaner, charger and the like to constitute such process cartridge) are removed from the image forming system and is replaced by a new one.
Here, an example of a technique for opening the developer supplying opening by removing the sealing member as disclosed in the U.S. Pat. No. 4,615,608 is applied to the developing apparatus of FIG. 1(A) is shown in FIGS. 1(B) and 1(C).
FIG. 1(B) is an exploded perspective view showing the above-mentioned slit 22 of the partition plate 21 of the developer container portion 20 and a sealing member 30 for sealing the slit opening.
The sealing member 30 comprises a ribbon-shaped soft sealing member (sealing ribbon) for covering the elongated slit 22 of the partition plate 21 from outside to seal the slit opening, and is adhered to a periphery 25 of an upper or outer surface of the partition plate 21 surrounding the slit opening 22 by means of an appropriate adhering method such as heat sealing, impulse sealing, high-frequency welding and the like. The sealing member 30 has an extension at its one side to form a bent portion 30A which has a free end portion 30B acting as a gripping portion, which free end portion 30B is protruded outwardly from abutted flanges 13 and 24 of the respective developing container portion 10 and developer container portion 20 at one end of the developing apparatus to provide the gripping portion, as shown in FIG. 1(C).
In use, by gripping the gripping portion 30B and by pulling the bent portion 30A toward outside of the apparatus against the adhesive force between the sealing member 30 and the periphery 25 of the partition plate 21, the sealing between the sealing member 30 and the periphery 25 is gradually released from an end of the slit 22 opposite to the gripping portion 30B toward an end of the slit near the gripping portion, and finally, when the whole of the bent portion 30A and sealing member 30 is completely extracted out of the developing apparatus, the slit opening 22 is completely opened, thus supplying the developer from the developer container portion 20 to the developing container portion 10 through the opened slit opening 22.
However, the above-mentioned sealing has the following drawbacks:
(1) It is needed for a strong force to open the slit opening 22 by separating the sealing member 30 from the periphery 25 (FIG. 1(B)) of the partition plate 21.
(2) In order to obtain the so-called "easy peel", it is difficult to control the adhesion strength (between the sealing member 30 and the periphery 25); therefore, if the peeling force is selected to be weaker, the adhesion strength will be insufficient, with the result that there arises the danger of unsealing the slit opening particularly when the surrounding temperature is lowered, thus causing the leakage of the developer and the like.
(3) Due to the crack in the sealing member and/or damage of the sealing member occurred in the sealing operation, there is a risk of tearing the sealing member during the unsealing or peeling operation, which results in making the use of developing apparatus impossible.
(4) Due to the adhering allowance of the sealing member 30, a width W.sub.30 of the sealing member must be larger than the width W.sub.22 of the slit opening, with the result that when, the sealing member is adhered to the developing apparatus, the bent portion 30A of the sealing member may be nipped by the container portions and/or may be adhered to the body of the sealing member if the adhesive or molten resin sticks to the bent portion, which leads to make the removal of the sealing member impossible.
(5) In the construction as shown in FIG. 1(B), since the flange portions 13 and 24 by which the developing container portion 10 and the developer container portion 20 are interconnected must be positioned outside the sealed area between the sealing member 30 and the partition plate 21, the flanges are obliged to be protruded from the body of the developing apparatus, thus preventing the compactness of the whole apparatus. Particularly, in view of the above problem (4), the distance between the interconnected flange portions and the sealed area must be relatively large, which results in difficulty in compactness of the developing apparatus more and more.
(6) When the sealing member 30 is peeled from the partition plate, since the flocculating destruction occurs in the sealed area on the periphery 25 of the partition plate 21, fine particles of the solidified adhesive may be mixed into the developer.
(7) The width W.sub.22 of the slit opening 22 once set cannot easily be altered or adjusted, since the slit in the partition plate is formed by the blanking die or injection mould.
In order to eliminate the above-mentioned drawbacks, the following arrangement has been proposed (refer to the Japanese Patent Application Laid-Open No. 59-13262). That is to say, according to such an arrangement, in the construction of FIGS. 1(A) and 1(B), the partition plate 21 is omitted, and the sealing member 30 covers the whole opening of the developer container portion 20 and is adhered to the flange 24 of the container portion 20. And, the sealing member has a gripping end portion having the same width as a desired width of a slit to be formed in the sealing member, and the sealing member is formed to be easily torn only in the direction of the gripping portion or, seam lines are formed in the sealing member along the extension of the side edges of the gripping portion. With this arrangement, by pulling the gripping portion, a portion of the sealing member corresponding to the width of the gripping portion is separated or torn from the remaining portion of the sealing member to create an opening or slit in the sealing member, which acts as a developer supplying opening.
However, in this arrangement, as the sealing member is torn, the sealing strip portion being torn may be gradually narrower or wider. In such a case, the width of the slit opening formed in the sealing member is not uniform in a longitudinal direction thereof, thus occurring the uneven supply of the developer along the slit opening. Further, it was found that, during the tearing operation, the sealing strip being torn was sheared on the way, thus making the formation of the slit opening impossible.